1. Field of the Invention
The present invention relates to a refrigerating system and, in particular, to a compressor driving system in such a refrigerating system for use in a vehicle with an engine, for example, an automotive refrigerator van.
2. Description of the Prior Art
In order to cool, chill or refrigerate food, drinks, and/or others, a refrigerating system is provided in a vehicle, for example, an automobile. A dedicated vehicle is also known as a refrigerator van or chill car for transporting cold, chilled, or refrigerated food.
The refrigerator system for use in a vehicle usually has a refrigerant circuit which comprises a refrigerant compressor for compressing refrigerant, a refrigerant evaporator for cooling a refrigerator compartment, and piping for refrigerant flow path. The compressor is usually driven by an engine of the vehicle.
In the system, the engine must be driven for cooling the food and/or drinks in the refrigerator compartment even during the period when the vehicle stops.
However, it is undesired to drive the engine for a long time, for example, throughout the night, when the driver is sleeping.
Therefore, another compressor of a motor driven type is usually provided as a standby compressor, especially, in the dedicated vehicle. The standby compressor is driven by use of the commercial AC power source.
However, the additional provision of the standby compressor complicates piping of the refrigerant circuit.
Further, it is difficult to carry out accurate temperature control in the refrigerator system because the refrigerant compressor is driven by the engine which often varies in R.P.M. when is driven.
On the other hand, an air conditioning or cooling system is usually provided in the vehicle for cooling the passenger compartment. A refrigerant compressor and an evaporator in the air conditioning system are commonly mounted on the vehicle independent from the compressor and the evaporator for the refrigerator system on the vehicle. Although the remaining refrigerant circuit elements, for example, a refrigerant compressor and a receiver and dryer device, are common in the air conditioning and the refrigerator systems, use of three compressors complicates the piping of the refrigerant circuit for the air conditioning and the refrigerator systems.